For 20 years, Bart McIntyre has tracked white supremacist movements, even spending two years undercover in Alabama to penetrate a violent young band of criminals who called themselves the Confederate Hammerskins.

Away from his wife and young daughter, McIntyre took the alias "Mark," attended Ku Klux Klan rallies and educated himself in racist propaganda. He and a law enforcement partner ultimately helped build criminal cases that sent more than 10 men to prison for their involvement in the murder and vicious beatings of black men in the Birmingham area in the early 1990s.

Now, as McIntyre prepares to retire from the Bureau of Alcohol, Tobacco, Firearms and Explosives, he and other analysts are warning that the threat from hate groups and splinter organizations connected to the Klan should not be underestimated, especially at a time of economic unrest.

"In society, you have a very small number of people who are going to push the envelope and take it to the next step," said McIntyre, the resident ATF agent in charge in Roanoke.

Veteran investigators say they have advocated for increased attention to the problem since late September, when the nation's economic troubles widened, giving white supremacists a potent new source of discontent to exploit among potential recruits.

The number of U.S. hate groups has increased by 48 percent, to 888, since 2000, according to experts at the Southern Poverty Law Center, an independent organization that monitors racist movements.

Although questions persist about the ability of such groups to carry out violent plans, several recent national developments have combined to worry analysts, said Mark Potok, chief of the law center's Intelligence Project. In addition to the economic downturn, he cited rising immigration, demographic changes that predict whites will not be a majority within a few decades, and what some might see as "the final insult -- a black man in the White House."

The election of Barack Obama, who will become the first African American president when he is inaugurated Jan. 20, prompted a short-term burst of hateful incidents including racist graffiti, cross burnings and violence from New York to California, according to news reports and criminal indictments. On Wednesday, the U.S. attorney in Brooklyn indicted three Staten Island men on hate crimes charges, alleging that they assaulted black residents "in retaliation for President-elect Barack Obama's election victory."

Last week, intelligence officials assessing security threats to Obama's inauguration found no evidence of an organized plot, although they expressed concerns about "individuals on the extremist fringe of the white supremacist movement" who might see the event as an ideal time to make a powerful statement.

Law enforcement officials declined to discuss the impact of Obama's victory, but several recent criminal cases investigated by the FBI and the ATF touch on the issue. In Tennessee, two young men -- one with ties to the Southern White Alliance, an offshoot of the Imperial Klans of America -- were arrested in October and charged with conspiring to threaten and kill African Americans. Daniel G. Cowart and Paul M. Schlesselman carried a short-barreled shotgun, a .357-caliber handgun and cases of ammunition across state lines as part of the alleged plot.

Authorities say the men planned to overtake a predominately African American school, kill scores of people, and then attempt a drive-by attack on Obama while wearing white top hats and tails, according to government court filings. Cowart and Schlesselman have pleaded not guilty and are being held without bond until their trial.

"They sound crazy, like a really bad movie -- Quentin Tarantino gone awry," Potok said. "You listen to that, and you say, 'In a hundred thousand years, they never would have reached Obama.' But the reality is, they might have walked into a black high school and killed 20, 30, 40 people before anybody knew who they were."